Centrifugal electric pump for suction of aeriform fluids with silencing device

ABSTRACT

A centrifugal electric pump for suction of aeriform fluids includes an electric motor equipped with a shaft; a cylindrical suction box provided with an inlet for the aeriform fluid, one or more outlet openings arranged on the lateral wall thereof and with a closing cover; at least one fan driven in movement by the motor, arranged for sucking a flow of air from the inlet, centrifuge it and discharge it outside the suction box through the one or more outlet openings, a silencing device arranged inside the suction box. The silencing device includes an annular deflector, placed in front of the outlet openings, so as to interrupt the direct path of the flow of centrifuged air between the at least one fan and the outlet openings, and arranged for creating a shaped annular damping chamber for the flow of centrifuged air, open towards the suction inlet.

The present invention relates to the sector of machine tools for handling aeriform fluids.

In particular, the present invention relates to single- and multistage centrifugal pumps and suction devices driven by an electric motor, particularly suitable for use as vacuum pumps in vacuum cleaners and floor washers, used to clean surfaces by sucking up air containing dust or liquids, in domestic as well as in industrial and professional appliances.

Conventional centrifugal electric pumps for the suction of aeriform fluids essentially comprise a high-RPM electric motor and a cylindrical suction box with an inlet through which the fluid is sucked, and at least one outlet opening for discharging said fluid. The movement of the fluid through the chamber inside said box is induced by at least one impeller, or fan, contained therein.

Said fan is arranged for sucking a flow of air through the suction inlet, located centrally in relation to a bottom of said box, centrifuge it and return it to the environment through a plurality of outlet openings arranged on the lateral surface of said suction box or, alternatively, in a tangential version of the pump, through a single outlet opening connected to a tangential outlet pipe.

Such a pump is normally used in vacuum cleaners or floor washers to create a negative pressure inside a tank for collecting dust or liquid contained in the flow of air sucked into the device.

Such centrifugal electric pumps for aeriform fluids have a major drawback: when in use, because of the high turning speed of the motor, the air is sucked into and subsequently discharged from the appliance at high speeds. The impact of the air against the outlet openings and the turbulence induced inside the suction chamber by the rotation of the fan give rise to high noise levels.

Said noise unfortunately persists all the time the appliance is in use, disturbing the user, polluting the working environment and affecting any other people in the vicinity.

The object of the present invention is to overcome said drawback by means of a centrifugal electric pump for the suction of aeriform fluids with a silencing device that reduces the noise it generates when in use.

Another object of the present invention is to produce a silencing device that is easy to install in any type of suction box for said pumps, avoiding or reducing the need for additional fixing means and containing the manufacturing costs.

These objects are achieved with a centrifugal electric pump for suction of aeriform fluids comprising:

-   -   an electric motor equipped with a shaft;     -   a cylindrical suction box provided with an inlet for the         aeriform fluid positioned centrally with respect to a bottom of         said box, with one or more outlet openings arranged on the         lateral wall thereof and with a closing cover, also arranged for         acting as base for said motor;     -   at least one fan, splined onto said shaft and driven in movement         by said motor, arranged for sucking a flow of air from said         inlet, centrifuge it and discharge it outside said suction box         through said one or more outlet openings,         characterized in that it comprises a silencing device arranged         inside said suction box, wherein said silencing device comprises         an annular deflector placed in front of said outlet openings, so         as to interrupt the direct path of the flow of centrifuged air         between said at least one fan and said outlet openings, and         arranged for creating a shaped annular damping chamber for the         flow of centrifuged air, open towards said suction inlet.

According to one aspect of the invention, said annular deflector forms an acute angle α with said lateral surface of said suction box, so that said shaped annular damping chamber has a triangular or trapezoidal cross section.

According to a preferred aspect of the invention, the edge of said annular deflector with larger circumference cooperates with the lateral wall of the suction box to produce a joint with interference fit.

According to another preferred aspect of the invention, said annular deflector comprises a shaped wing bent parallel to said closing cover.

A preferred method for obtaining and installing the silencing device in the cylindrical suction box of a centrifugal pump for the suction of aeriform fluids comprises the following stages:

-   -   preparing a bottom for a cylindrical suction box for a         centrifugal pump;     -   widening the central hole serving as a suction inlet;     -   using a press to deform said bottom in order to make it suitably         conical, obtaining an annular deflector in the shape of a         truncated cone with a shaped wing bent parallel to said closing         cover;     -   positioning said deflector on the base of a motor of a         centrifugal pump for the suction of aeriform fluids, and fixing         it in place by interference against the cylindrical lateral wall         of the suction box.

The invention offers the following advantages.

The main advantage lies in a considerable reduction in the amount of noise usually generated inside the suction box of said centrifugal electric pump for the suction of aeriform fluids.

The annular deflector, arranged and shaped so that the outlet opening(s) come to be downstream from the flow of air sucked into the appliance, shields said outlet openings, preventing the flow of air from being discharged directly, and orthogonally as is normally the case, at maximum speed.

The shaped annular damping chamber, delimited laterally by said annular deflector and open on the side facing said suction inlet, also only allows the flow of air to reach the outlet openings from below, further damping its speed and the turbulence created by the fan inside said suction box.

Another advantage lies in the simplicity with which said annular deflector cooperates with the lateral wall of the suction box to achieve a joint with an interference fit, possibly even without any need for additional fixing means, thereby containing the manufacturing costs and assembly times.

The method for manufacturing the silencing device is also highly advantageous, involving the reuse, after simple processing steps, of the same closing cover for the suction boxes of known types of centrifugal pumps used for the suction of aeriform fluids, readily available without having to manufacture any additional components.

These and other advantages will become more apparent below, in the description of a preferred embodiment of the invention, given here as a non-limiting example with reference to the figures, wherein:

FIGS. 1 and 3 show a cross view and an axonometric cross sectional view, respectively, of a centrifugal pump for the suction of aeriform fluids with a silencing device according to the invention;

FIG. 2 shows a cross sectional view of a detail of the suction box without the impellers, wherein the silencing device is made transparent.

With reference to FIGS. 1-3, the figures show a centrifugal electric pump 1 for the suction of aeriform fluids with a silencing device according to a preferred embodiment of the present invention.

Said electric pump 1 essentially comprises an electric motor 2 with a drive shaft 3, a suction box 4, and fans 8 arranged for moving a flow of air F.

Said suction box 4 has a cylindrical shape and comprises a circular bottom 4′ with a suction inlet 5 located at its centre, and a lateral surface with a plurality of outlet openings 6.

The bottom 4′ and the lateral wall 4″ of the box 4 are made of a single, suitably shaped and perforated sheet of metal.

Said box 4 is closed at the top by a cover 7 arranged for serving as a base for said motor 2 as well.

Said fans 8 are splined onto said drive shaft 3 and driven by said motor 2.

The silencing device comprises an annular deflector 9, arranged inside said suction box 4 in front of said outlet openings 6.

Between them, said annular deflector 9 and the lateral wall 4″ of said suction box 4 laterally delimit a shaped annular damping chamber 10 for the flow F of centrifuged air, wherein said chamber 10 opens towards said suction inlet 5.

The annular deflector forms an acute angle α with said lateral wall 4″ of said suction box 4, so that said shaped annular damping chamber has a triangular or trapezoidal cross section.

The edge 11 of said annular deflector 9 with the wider circumference cooperates with the lateral wall of the suction box to achieve a joint with an interference fit.

In particular, said annular deflector 9 comprises a shaped wing 12 bent parallel to said closing cover 7.

A preferred method for obtaining and installing the silencing device in the cylindrical suction box 4 of a centrifugal electric pump 1 for the suction of aeriform fluids comprises the following stages:

-   -   providing a bottom 4′ of a cylindrical suction box 4 for a         centrifugal pump 1;     -   widening the central hole serving as a suction inlet 5;     -   using a press to deform said bottom 4′ so as to create a         suitable acute angle α of conicity, obtaining an annular         deflector 9 with a shaped wing 12 bent parallel to said closing         cover 7;     -   positioning said deflector 9 on the base of a motor 2 serving a         centrifugal electric pump 1 for the suction of aeriform fluids         and fixing it by interference between one of its edges 11 and         the cylindrical lateral wall 4″ of the suction box 4.

The operation of the silencing device is as follows.

The flow of air F is drawn through the suction inlet 5, centrifuged by the fans 8 located inside the suction box 4 and sent towards the outlet openings 6.

The annular deflector 9 deviates the flow of air F, intercepting its direct discharge perpendicular to the outlet openings 6. Said flow of air F is carried under the chamber 10 laterally delimited by the annular deflector 9 forming an acute angle α with the cylindrical wall 4″ of the suction box 4, and it is obliged to reach the outlet openings 6 by travelling through the annular chamber 10 with a sloping wall and consequently with a gradually narrowing cross section.

The table below compares the noise levels recorded on two centrifugal pumps for the suction of aeriform fluids, connected to a vacuum measuring device with a calibrated fluid inlet of selectively variable dimensions, wherein one of said pumps is provided with a silencing device according to the invention.

Noise level Difference Inlet Current Power Vacuum Flow Air Noise level without in noise size intensity absorbed Speed pressure rate power Efficiency with silencer silencer level mm A W RPM mmH2O mbar L/sec W % Min dB Max Min dB Max Min dB Max 48 12.4 298 11.360 29 2.8 23 6 2.2 70.5 70.6 74.7 74.9 −4.2 −4.3 40 12.4 298 11.340 60 5.9 23 14 4.6 69.9 70.1 74.4 74.7 −4.5 −4.6 30 12.5 300 11.230 159 15.6 21 33 10.9 69.2 69.4 73.5 73.7 −4.3 −4.3 23 12.4 298 11.290 311 30.5 17 52 17.4 67.0 67.2 71.5 71.8 −4.5 −4.6 19 12.2 293 11.450 431 42.3 14 59 20.2 66.4 66.6 69.9 70.1 −3.5 −3.5 16 11.9 286 11.760 527 51.7 11 57 19.9 65.7 65.9 69.0 69.2 −3.3 −3.3 13 11.4 274 12.130 615 60.3 7 42 15.4 66.0 66.2 68.0 68.2 −2.0 −2.0 10 10.8 259 12.620 702 68.8 5 34 13.3 65.2 65.4 68.3 68.8 −3.1 −3.4 6.5 10.3 247 13.230 783 76.8 2 15 6.2 66.6 66.8 67.9 68.4 −1.3 −1.6 0 9.7 233 13.880 917 89.9 0 0 0.0 67.4 67.6 67.3 67.6 0.1 0.0

The invention as described and illustrated enables the previously stated aims and objects to be achieved.

In practice, all the manufacturing details may naturally be replaced by other, technically equivalent solutions, and the materials, shapes and sizes may vary as necessary, without departing from the patent-protected scope of the invention as explained in the claims. 

1. A centrifugal electric pump (1) for suction of aeriform fluids comprising: an electric motor (2) equipped with a shaft (3); a cylindrical suction box (4) provided with an inlet (5) for the aeriform fluid positioned centrally with respect to a bottom (4′) of said box, with one or more outlet openings (6) arranged on the lateral wall (4″) thereof and with a closing cover (7) also arranged for acting as base for said motor (2); at least one fan (8), splined onto said shaft (3) and driven in movement by said motor (2), arranged for sucking a flow of air (F) from said inlet (5), centrifuge it and discharge it outside said suction box (4) through said one or more outlet openings (6), characterized in that it comprises a silencing device arranged inside said suction box (4), wherein said silencing device comprises an annular deflector (9), placed in front of said outlet openings (6), so as to interrupt the direct path of the flow of centrifuged air (F) between said at least one fan (8) and said outlet openings (6), and arranged for creating a shaped annular damping chamber (10) for the flow of centrifuged air (F), open towards said suction inlet (5).
 2. A centrifugal electric pump (1) according to claim 1, characterized in that said annular deflector (9) forms an acute angle (α) with said lateral wall (4″) of said suction box (4), so that said shaped annular damping chamber (10) has a triangular or trapezoidal cross section.
 3. A centrifugal electric pump (1) according to claim 1, characterized in that the edge (11) of said annular deflector (9) with larger circumference cooperates with the lateral wall (4″) of the suction box (4) to produce a joint with interference fit.
 4. A centrifugal electric pump (1) according to claim 1, characterized in that said annular deflector (9) comprises a shaped wing (12) bent parallel to said closing cover (7). 